Slope of yard sewer into septic tank. Minimum sewer slope

For slope of external and internal pipes sewerage in a private house, as well as for laying sewerage in an apartment, exact standards have already been calculated and the corresponding SNiPah recommendations have been submitted. However, very often for proper outflow it is necessary to calculate the optimal level of slope based on individual parameters, type of room, material and pipe diameter.

Let's consider SNiPs, recommendations and calculation formulas for what slope a sewer pipe should have for a length of 1 meter in different cases- in an apartment, private house, indoor and external network and depending on the material of manufacture sewer pipes.

For normal operation sewer system it is extremely important to do accurate calculations. What are the consequences of mistakes?

Too much slope will lead to accelerated outflow, which will be accompanied by loud noise. At the same time, the inner surface is quickly erased and self-cleaning slows down.
Insufficient level threatens to clog the system, especially if it does not contain fecal household pump. The location of a pipeline blockage is difficult to diagnose and repairs take a long time.

It is best when the movement of waste occurs at a speed of 0.7 -1 m/s. IN In the calculation process, it is necessary to take into account the diameter, material and fullness (hydraulic pressure) of the pipes.

SNiP

When designing a sewer system, it is customary to be guided not by formulas, but by the values given in SNiPs. Installation inside a building is subject to the requirements of Section 2.04.01-85, and outer gasket– section 2.04.04-85.

Different calculation methods are needed for multi-story buildings and large residential complexes.

All figures are given in the form of coefficients and measured in centimeters per linear meter. The designation in degrees is not used due to large errors in the installation process to a septic tank or sewer well, which are located at a distance of 10-12 m from the house. So, for a diameter of 40-50 mm and a septic tank distance of 12 m, a coefficient of 0.03 (3 cm/lm) is applied, and for a cross-section of 85-100 mm - 0.02.

Minimum permissible slope for outdoor and internal lines sewerage according to SNiP is 0.015; when the slope of sewer pipes is less than the minimum angle, solid particles remain in the pipe. On small areas– no more than 1 m, a coefficient of 0.01 is allowed.

Maximum slope outdoor and internal sewerage according to standards, it does not exceed 3% and generally depends on the flow speed; in plastic sewer pipes, a speed of up to 1.4 m/s must be maintained, otherwise the flow will be divided into fractions and solid particles will remain in the system.

Calculation for an apartment

For sinks, sinks, washbasins and bathtubs, pipes with a diameter of 40-50 mm with a slope of 2.5 cm to 3.5 cm per meter are selected. To drain wastewater from the toilet, the line diameter is 100 mm. Minimum value per linear meter - 0.012, and the norm is 0.02. During installation, a bubble or laser level is used.

Separately, the complex Callbrook-White formula can be used. It looks like this:

Sewerage in multi-storey buildings located vertically. The drains move along the diameter of the walls, and in the center of the flow - compressed air. With this flow, blockages almost never appear.

Calculation for a private house

For small volumes of wastewater, calculations are not necessary. The main thing is that the slope is not less than the minimum allowable according to SNiP standards.

It is important that the slope and cross-section of the sewerage contributed to the filling of the pipeline by at least a third of the diameter.

To increase maintainability and service life, it is recommended to use pipes made of the same material.

Typically, preference is given to sockets mounted against the flow in the main. If it is necessary to change the direction of flow, it is advisable to avoid sharp turns.

So, instead of one fitting for 90 o, it is advisable to use 2 x 45 o.

When forced external sewerage All plumbing is located below the level of the septic tank. Calculating angles along the entire length of the pipeline becomes irrelevant. It is only necessary that the sewage be fed by gravity to a single collector and pumped out from there. Find out what pipes are used for external sewage from this.

Second option– installation in the system after each plumbing fixture. We will tell you how to properly install a sewer system in a private house in this article.

Optimal values for an outdoor system

When laying an external sewer system, the point at which the pipeline exits the wall or foundation is taken as the basis. The rule is followed: the smaller the cross-section, the greater the slope. For normal outflow with a diameter of 110, 0.02 is enough, and for pipes 60-80 mm, 0.03 or more is needed.

There are 3 main factors to consider:

Relief. Drain wells are usually located at the lowest point of the site, so the natural slope of the trench is also added.
Pipeline depth near the septic tank should not be lower than the inlet hole in sewer well.
The slope should be rational so that you don’t have to dig a drainage basin too deep - this is both expensive and dangerous due to groundwater entering the septic tank.
Trench must be deeper than the freezing level of the soil.

Rules for installing internal pipelines

When laying, where all points are reduced to one riser, The drain volume is calculated in total for all devices, connected to the highway. Floor unevenness must be calculated so that the slope and height difference between the plumbing fixtures and the drain are consistent with SNiP standards.

During the design and installation process You need to pay attention to a few more points:

Natural shrinkage. The soil may be compacted by the action external factors, resulting in a change in slope.
It is advisable to install inspection hatches in certain areas in increments of 30-40 cm in case of clogging due to poor outflow. For the same purpose, specialists connect pipes at an angle of at least 120°.
Calculations are carried out starting from the outlet point of the sewer, but installation always occurs in reverse order– in the direction from the drain well.
The project is designed so that the line length is minimal. The shorter the line, the less likely it is to become clogged or break down.

The correct location of sewer drains allows you to avoid blockages and ensure a long service life of all communications.

The optimal calculation option is orientation to SNiP standards and accounting individual characteristics buildings and locations of bathrooms. Upon completion of installation, before digging the trench, all elements of the main line are checked for tightness and reliability of outflow.

In most cases, the sewer system is gravity-fed. This means that all drains leave on their own, under the influence of gravitational forces. But in order for them to move, the pipes must be laid not level, but with a slope, and with a certain one. We will talk further about what the slope of the sewer pipes should be.

Why do you need a sewer pipe slope?

Everyone has probably heard that sewer pipes must be laid with a slope, and even moreover, as determined by building codes - SNiP. Why is this so? Because it is necessary that the speed of movement of wastewater through the pipes be such that water and solid particles move together.

When installing or repairing an existing sewer system myself, I often make two mistakes:

What should the slope be?

How to understand what a pipe slope is? In SNiP it is written in fractions - in the form of decimals. It will look like this: 0.03 or 0.008. The numbers are deciphered as follows: this is the difference in heights of the two ends of a meter-long piece of laid sewer pipe. The number 0.03 means that one end of the meter pipe is raised by 3 cm. Accordingly, the number 0.008 means that one edge is raised by 0.8 cm or 8 mm.

The pipeline is usually much longer than one meter. You can calculate how much higher one end should be than the other by multiplying the selected slope by the length of the pipeline. For example, we will lay a sewer with a slope of 3 cm/m, its length is 25 m. This means that its far end will be lowered by 3 cm * 25 m = 75 cm.

Dependence on pipe diameter

Sewage systems are divided into internal - installed in an apartment or house, and external - which are laid on the street. In both cases, it is necessary to maintain the required slope of the sewer pipe. When they say that, they mean recommended sanitary standards index. It depends on the diameter of the pipes used: the smaller the cross-section, the greater the slope must be given.

Diameter of sewer pipes	Normal slope	Smallest allowed
50 mm	0.035 (3.5 cm)	0.025 (2.5 cm)
100 mm	0.02 (2 cm)	0.012 (1.2 cm)
150 mm	0.01 (1 cm)	0.07 (7 mm)
200 mm	0.008 (0.8 cm)	0.005 (0.5 cm)

The table shows the slope of the sewer pipe, which will provide normal work systems. If for some reason it is not possible to make the required slope angle (this happens in areas with complex terrain), the slope angle can be reduced to the specified limit norm. The chance of getting problems increases, but not much.

What to do if the slope is greater than required

Sometimes it is not possible to make the required slope - conditions vary. In this case, there are two solutions:

The first option is a cheaper device, but it involves frequent blockages in the pipes. Of course, with intensive use of sewerage ( a large number of water), there may not be any problems, everything can work without problems. But this is rather an exception. By the way, when using plastic pipes, the likelihood of blockages becomes lower - they have smooth walls, on which precipitation rarely forms. The second option is more expensive and labor-intensive, but it guarantees the functionality of the system.

How to maintain the required slope

Determining the slope of the sewer is not enough. It still needs to be maintained during installation. Most convenient option— presence of a special level with a protractor. If professional equipment no, you have to be cunning.

There are ways to control the angle of a sewer pipe using a regular level:

Having drawn a line on the wall with the desired slope, apply a building level to it and make a mark on the plastic in the place where the edge of the bubble is located. When placing the pipes, position them so that the bubble is in the desired position.
If you take a meter level, you can attach a pad of the required width to one side. This method does not work in short sections, but it is convenient to install a long pipeline.

Internal sewerage

When laying a pipeline, it is necessary to maintain a given slope and prevent deflections and sagging. By the way, when laying outlet pipes from different plumbing fixtures, it is necessary to withstand different slopes (see photo below).

When laying an internal pipeline, you can draw the required slopes on the wall and align the pipes along them. You should not focus on the floor level; it is better to mark a horizontal line. It’s easier to do this if you have a level; if you don’t have one, you can use a bubble level. After this, having calculated the required difference (described above), you “lift” the far end. Once again check the accuracy of the calculations and drawn lines. Afterwards you can begin installation.

In bathrooms and toilets, the required level is usually laid out using a thick sand-cement mortar. Anyway, then the pipe is finished off - a plasterboard box is placed, onto which the tiles are then glued. More modern version- laying pipes in a groove is not accessible to everyone - in panel houses The walls are not that thick. When laying sewer pipes from the kitchen, stands and wedges are often used. After the pipeline is laid with the required slope, it is fixed to the walls using special holders. They are installed in increments of no more than 40 cm.

Advice! When installing, turn the sewer pipes against the flow. This way there is less chance of leaking joints.

External sewerage

The sewage system on the site is laid in trenches. When laying the route, try to make it as straight as possible. Any turns are a potential place for a blockage to form. If you can’t do without turning, install a tee next to it, bring the pipe just above ground level and cap it with a sealed cap. This will be the right decision - you will be able to clean the plugs quickly and without problems.

When laying an external sewer, dig a trench with a flat bottom. The depth of the trench is 20 cm more than necessary - this is a place for a sand cushion. If the length is short and the drop is small, the bottom can be left as it is - flat. If the difference is large, you will have to form a slope. At this stage there is no need to maintain the tilt too much - do it approximately. Then the bottom is leveled, all stones and roots are removed, the holes are leveled, and compacted. There must be a flat, dense base.

Sand is poured onto the leveled bottom. It must be sprinkled in layers of 5 cm, leveled, compacted (spill with plenty of water). By laying 4 layers in layers, we get a cushion of 20 cm. Pipes are laid in the sand, forming a given slope. The slope can be checked with a long building level(1.5-2 meters or more). If this is not the case, you can tape it to a long, flat strip (beam) in the middle with tape. bubble level. This way you can achieve minimal error.

After the pipe is laid and its slope is checked, it is covered with sand. It should cover it almost halfway. The sand is carefully leveled and spilled. After this, the pipe is covered 1/3 with dense sand (the level can be higher). Then you can fill it with soil.

July 7, 2016
Specialization: philological education. Work experience as a builder - 20 years. Of these, for the last 15 years he led a team as a foreman. I know everything about construction - from design and zero cycle to interior design. Hobbies: Vocals, psychology, quail breeding.

In the photo - obviously incorrect installation sewer pipes - they have almost no slope.

Greetings, my dear readers. We all love modern comfort, including its part regarding hygiene. It can be very disappointing when it is violated, but often we ourselves are to blame for this. For example, we often don’t think about what the slope of a sewer pipe should be so that the wastewater and waste from our life is discharged normally.

Please note that in the vast majority of cases, gravity sewerage is installed in our apartments and houses. Based on this, it is extremely important to choose optimal slope for each of the outlet pipes. If the angle is small or does not exist at all, the cost of the mistake will be high - this will lead to constant blockages; if it is too large, the system will leak.

The value of the angle of inclination for sewer pipes

First of all, I want to warn you right away so that you don’t get lost in the units of measurement. In all regulatory, technical and advisory documents, the slope of sewer pipes is displayed not in degrees, but in centimeters, relative to the initial (upper) and conditionally final (lower) points of the system.

I'll tell you a small, but very, very interesting secret. This is explained quite simply. The concept of “degree” relative to the Earth’s axis, as well as the location of objects on its surface during construction own home(very, very small in comparison with the total surface of the planet), not very effective.

The resulting values are too insignificant. If you are guided by degrees when laying sewer pipes, then you simply risk taking them somewhere in the wrong place.

Effect of pipe inclination

The wastewater, by definition, has never been clean. Especially now, when the sewer system disposes of the increased volume of waste from our life.

So, laundering dirty dishes, you discharge cleaning agents, fats, food particles into the pipeline. Over time, on the walls of the system increases sticky coating. It promotes overgrowth of pipes. Their correct slope allows the sewer to clean itself.
Flowing inside the network at a speed set precisely by the slope of the pipes, the wastewater washes out a significant amount of waste, thereby preventing clogging of the system.
I especially draw your attention to this dependence: the greater the slope of the sewer pipe, the higher the speed of liquid flow in it. This means that the degree of filling of the pipe decreases.

Why is it bad to reduce too much or too little?

In connection with what I wrote above, you may have an idea: place the pipes at as high an angle as possible so that the waste is discharged faster. However, I warn you right away - this thought will be unsuccessful:

If the drain is too steep, the pipes will silt, because... will begin to reset very quickly. They simply will not have time to flush out solid waste particles. They will begin to settle on the walls of the pipes.

In addition, water locks in siphons will break. Consequently, air from the sewer will begin to penetrate into the premises. I won’t remind you how “pleasant” its smell is.
It is extremely undesirable to leave metal sewer pipes unfilled for another reason. In an aggressive environment, the flow of oxygen to their inner walls leads to corrosion. As a result, the service life of the pipes is reduced.
Excessive slope increases the noise of the pipeline.
It also reduces the system's ability to clean itself, which leads to waste settling and pipe clogging.

I cannot help but note the opposite situation: insufficient slope of the pipes leads to a decrease in the flow rate. This also causes blockages.

In an apartment, it is almost impossible to measure the flow of liquid in the sewer on your own.
Therefore, I advise you to adhere to the values stated in the regulatory documents.
Thus, the recommended SNiP speed of wastewater in apartments should be 0.7-1 m/sec.

Regulatory and reference documents

What should be the correct slope of sewer pipes? The answer to this question is given by regulatory documents:

For small-diameter pipes in the internal part of the sewer system, clause No. 18.2 of SNiP No. 2.04.01/85 “Internal water supply, as well as sewerage of buildings” applies. It states that non-calculated branches of networks with a cross-section of 4-5 cm should be laid with a slope of 0.03, with a cross-section of 8.5 and 10 cm - with a slope of 0.02.
An external sewer system requires a larger network. This is what I know in this part about the slopes of sewer pipes according to SNiP No. 2.04.03/85, paragraph No. 2.41 “Sewerage. External structures and networks": the minimum slope for pipes with a cross-section of 15 cm should be 0.008, and 20 cm - 0.007.

When carrying out repairs, you may need to make the network slope less. This is what I can advise you in relation to internal sewerage and for unmetered sections of the pipeline. SNiP No. 2.04.01-85, paragraph No. 18.2 states the following provision:

The calculation of the sewerage pipeline must be carried out by setting the fluid flow speed (V, in meters per second) and the filling (H/d) so that the condition is valid: V√H/d≥K. In this case, K for pipes made of plastic and glass should be equal to 0.5, and for networks made of other materials – 0.6.
The water flow speed must be at least 0.7 m/sec, and the pipe filling must be at least 0.3. In other words: in theory, if you calculate the volume of waste, then the filling and determine the speed of the liquid, you can get some other result.
However, I hasten to warn you: in SNiP No. 2.04.03/85 for external sewer pipelines there is a direct explanation regarding networks with a cross-section of 15-20 cm.

It voices the following conditions: based on local conditions and with proper justification for individual sections of the network, it is permissible to operate with the following slopes: for pipes with a cross-section of 20 cm - 0.005, for analogues with a diameter of 15 cm - 0.007.

I can make you happy. This means very interesting thing. Namely: if you have a reinforced concrete justification “very, very necessary” and a great desire to implement it, then there are no barriers to its implementation. You can save as much as 2 mm of slope on every meter of pipes with a cross-section of 20 cm.

According to paragraph No. 18.3 of SNiP No. 2.04.01/85, the highest slope of networks should not be more than 0.15 (excluding branches from plumbing fixtures up to 150 cm in length).

In other words, the slope should not be more than 15 centimeters for each meter of the network. If you exceed this figure, the pipeline will silt, since liquid waste will quickly leave, but solid fractions will remain.

Having rummaged through my technical library, I found a very useful thing for you from the reference book by A. and N. Lukin “Tables for hydraulic calculations of sewer siphons and pipelines.” In it, the cross-section and slopes of sewerage pipes are connected with plumbing fixtures.

Plumbing fixture	Diameter of the drain pipe, in millimeters	Slope, in centimeters per meter of pipe	Distance between the central drain and the siphon without ventilation, in meters
Bath	40	3	1-1.3
Bath, shower, sink (combined drain)	50	4.8	1.7-2.3
Shower	40	4.8	1.5-1.7
Toilet	100	2	Until 6
Bidet	30, 40	2	0.7-1
Washing	30, 40	3.6	1.3-1.5
Sink	40	1.2	0-0.8
Central riser	100
Branches from this riser	65-75

How to calculate the slope of sewer pipes yourself

You can independently find the value of the pipe slope by arranging the sewer system in your house with your own hands. I will tell you how to do this further.

Definition of slope

The main difficulty you will encounter as non-professional builders is that the measure of the slope is not clear. In SNiPs and reference books, which are guidelines for action for any builder, fractions are shown, for example 0.035 or 0.007. Most likely, you are used to using degrees and will not understand what slope of the pipes these numbers indicate.

I hasten to reassure you, everything here is extremely simple: these fractions show the ratio of the height of the depression to the meter length of the pipes. The easiest way to operate the parameter is in centimeters, for example 3.5 cm per 1 m or 0.7 cm per 1 m, as in the examples I gave above.

The length of the network in meters when multiplied by the slope value will give you the total height along the entire length of the branch.

Let me give you an example:

Let's say the total length of the pipeline is 6 meters and its slope is required to be 0.08.
Therefore, between the beginning (closest to the drain) and the end (entrance to the riser) of the pipe there should be the following difference: 6∙0.08 = 0.48 m or 48 cm.

How to calculate the fullness of pipes

The main parameter that should be followed when laying a sewer pipe is its fullness. You can determine it according to the formula: u=H/d. In it:

H is the height of the drain level in the pipe;
d denotes its diameter.

Wherein:

when u=0, it means that the pipe is empty;
when u=1, then it is completely filled;
The optimal values for fullness (K), at which the drain works most efficiently, is a plug of 0.5-0.6.

Such a range is explainable different characteristics pipe manufacturing materials and the level of potency to create a demarcating layer held near their internal walls.

For example, plastic and glass pipes have smoother inner walls, their fullness should be 0.5.
Cast iron, asbestos-cement, and ceramic analogues have a higher roughness; for them, the optimal value is 0.6.

The filling values I have given will allow waste to flow at a speed of about 0.7 meters per second. It will allow solid fractions to remain suspended and not settle on the walls of the pipes.

Summarizing all of the above, I bring you to the idea that you need to calculate the design characteristics of the pipeline using the formula K≤V√u. In it:

K - is the optimal degree of fullness (0.5-0.6);
V - indicates the speed of waste flow;
√u is Square root from the fillability of pipes.

How to measure the required angle

As you already understand, the minimum network slope in apartments depends on the cross-section of the pipes being laid. So, for 50 mm products it should be 3 centimeters per 1 meter of their length, for 85 and 100 mm - 2 centimeters.

You may be puzzled by the question of how to set the slope of a sewer pipe so that there is no mistake. After all, floors do not always have absolutely correct horizontality. I strongly recommend that you use a laser or bubble level for this.
I also advise you to tighten the marking cord. You can use it when the branch enters the riser and as a reference vertical.

Then calculate the depression angle as the arcsine of the depression ratio.
Next, subtract the resulting angle from 90.
The result will be the angle at which the end of the pipe should enter the riser.

Below I publish for you another table with optimal and minimum slopes of sewer pipes.

Slope for external sewer pipes

In the table below I show the correct slopes for external sewer pipes with a large cross-section relative to the internal part of the system.

Under special conditions the instructions imply the need to build a system when some reason prevents the optimal slope from being achieved. In other words, this is the minimum acceptable degree of reduction of external sewer pipes.

As I already wrote, there is a maximum value for this parameter. It is equal to 0.15. If the slope is more than 15 cm per meter of pipes, the drainage system will function ineffectively. The network will begin to silt if the liquid is discharged too quickly and will quickly become clogged.

Summarizing everything I have written and relying on SNiPs, I have outlined for you several important provisions and rules. Follow them when laying sewer pipes in your home.

Be sure to make a plan before starting work.
The optimal level of reduction of sewer pipes ranges from 1.5 to 3 cm per meter of network. For example, for every meter of length of a product with a cross-section of up to 50 mm, the slope should be 3 cm. For analogues with a diameter of 100, 110 mm, it should be 2 cm.
The maximum value (for both external and internal gravity sewerage) is the total decrease in the pipeline from its beginning to its end, amounting to 15 degrees.

When determining the level and angle of the outer part of the system, take into account the soil freezing limit in your region.
If you doubt the decision you have made, check the values obtained using the formulas and tables I have published.
When installing a sewer system (not combined with a toilet), you can make the fill factor, and based on it, the slope of the pipes, not very strong. The wastewater discharged from this room contains little abrasive suspended matter.
When calculating the slope angle, take into account other features of the system area. For example, load characteristics. When wastewater is discharged from an ordinary washbasin, you do not have to worry about silting. You can make the slope relatively large, but such that the hydraulic locks in the siphons do not break off.
I urge you to distinguish between the methods of installing sewer pipes in an apartment and in your own home.

In the second case, it is often used vertical installation outlet communications. Let me explain what this means: it extends strictly vertically from the plumbing fixture installed pipe, which interfaces with a highway laid at a given slope.

This method is used, for example, when plumbing fixtures are located in the residential attic of your own home. Another feature of working in a private house: often the installation of its external sewer system begins immediately after installation internal systems. In other words, there is no buffer in the form of additional floors between the internal and external parts of the sewer system.

In order to reach the required angle when installing pipes, I advise you to dig trenches already on a slope, then pull the cord along them. The same recommendation is valid for apartment floors.

Conclusion

When installing a drainage system special meaning has a sewer pipe slope of 110 mm or another diameter. I warn you in advance - if you do not take care of this at the system design stage, sad consequences await you in the future. The video in this article reinforces my words.

If you have any questions, ask them in the comments. I will be happy to answer them.

July 7, 2016

If you want to express gratitude, add a clarification or objection, or ask the author something - add a comment or say thank you!

In order to understand what the slope of the sewer pipe should be, it is necessary to calculate key parameter speed of sewage flow. Minimum speed - 0.7 m/s. All details are indicated in regulatory document SNiP.

There is a special formula with which you can calculate the parameters: V √ H/d ≥ K.

V is the speed of movement of wastewater;

H - degree of filling;

d - diameter;

K is the coefficient (in the case of glass and plastic pipes it is 0.5, for a pipeline made of another material it is 0.6).

If approximately, for each linear meter the pipeline should have a two-centimeter deviation. That is, for a pipe with a diameter of 40-50 mm, the slope of the sewer pipes per 1 linear meter is 3 cm. The slope of the sewer pipe is 110 mm 2 cm per meter. We recommend that you take into account the diameter, length, number of joints, number of turns of the pipeline, as well as the number of connected plumbing fixtures.

It is also important to consider the occupancy of structures. It depends on the number of people living in the house. How more people lives, the greater should be the occupancy of the installation. Formula for calculating fullness: y=H\D (H - level height, D - pipe diameter). The optimal fullness value is 0.5-0.6. It depends on the material from which the pipe is made. The glass and plastic pipe has a fullness of 0.5 due to smooth surface, nozzles made of glass and ceramics have a fullness of 0.6 due to the rough surface.

The wastewater system is an integral part of any home. In order for it to function correctly, you need to arrange it correctly, that is, choose the right angle at which it will be laid. Many people ask a well-founded question whether, according to SNiP, a sewerage slope of 1 meter will be sufficient or whether it needs to be made larger (or maybe smaller). Let's figure it out.

On a note! Even if you install a wastewater system under right angle, this will not guarantee normal and durable operation of the sewer system. Since there are a number of other points that need to be taken into account when installing it: location (pipeline layout indoors or outdoors), configuration, diameter and material of pipes.

Why is the tilt angle needed?

Why do we need a very specific angle of inclination of the wastewater system? Maybe it’s enough to just lay the pipes and not “bother” about how to make the sewerage slope 1 meter - the recommended values according to SNiP?

The main arguments for installing a sewer system at a certain angle:

Without it, the liquid will begin to stagnate in the pipes (and this is not good).
The sewerage system must function without any failures, despite the impossibility of predicting the consistency and nature of the wastewater.
The main purpose of arranging a slope is the desire to practically minimize the possibility of settling of solid fractions (or sludge) on the walls of the laid pipeline.
Ensure silent operation of the system, while preventing backflow of wastewater and eliminating bad smell directly indoors.

Too little slope or too much - which is better?

The most important thing is to determine exactly the minimum slope, since if it is too small wastewater will not leak out completely. As a result, you will inevitably end up with clogged pipes and all the ensuing consequences.

Fine. Maybe then make a large slope and be sure that everything is in order with the leakage of liquid and not have to calculate the minimum angle so that the slope of the sewer pipe by 1 meter - the recommended values according to SNiP - is observed? No, it's bad again. This is not an option. The fact is that if the slope is too large, large fractions are absolutely guaranteed to accumulate in the pipe and contribute to the formation of a blockage. The fact is that with a very large slope, the liquid quickly flows out, and to remove solid elements it takes more time (and there is nothing to wash them off with). As a result, the pipe is clogged and you panic.

It turns out that we need to find a “golden mean”, namely, determine the minimum angle of inclination of the wastewater system so that it functions well. If the design and installation of the sewer system are carried out strictly according to the standards of such a document as “ Building codes and rules”, that is, the sewerage slope of 1 meter (SNiP recommended values) is maintained, this will significantly increase the service life of the system that removes wastewater, and, naturally, the quality of its work.

Calculate the minimum angle of inclination

To determine the minimum angle of inclination, it is necessary to perform mathematical calculations using a certain formula. Here it is - V√H⁄D≥K: V - liquid drainage speed (optimally, it is 0.7 m/s); H - waste liquid level (that is, it determines the degree of filling of the pipeline and should be about 50-60%); D - pipeline diameter; K is the pipeline slope coefficient (optimally, it should vary from 0.5 to 0.7; that is, the closer to 1, the better).

Important! The degree of filling of the pipeline should not be less than 1/3.

Pipeline slope coefficient

This indicator can be determined in two ways:

Calculate it yourself using the formula - H/D.
Refer to reference material.

On a note! The value of this coefficient indicated in the reference book is directly dependent on the material from which the pipes are made: 0.5 - for glass and plastic; 0.6 - for materials such as cast iron, asbestos cement or steel. Also, do not forget about the degree of roughness of the inner surface of the pipe, which negatively affectsK.

It is known from practice that approximately a slope of 20 mm (per 1 meter of sewerage pipeline) will be sufficient.

Pipe diameter

If you don’t want to make any calculations, you can do without them: it is possible to determine the required slope of the sewer system depending on the diameter of the pipes. Practical, convenient and fast.

Naturally, all this can be done if the diameter is selected in such a way that the conditions for pipeline fullness (50-60%) and fluid velocity (0.7 m/s) are met. Otherwise, nothing will work.

As a rule, the calculation simply comes down to choosing a certain diameter (200, 150 (160), 100 (110), 80, 50 mm) and specifying the angle of inclination accordingly.

Important! Don't forget about the margins of error.

In SNiP, depending on the diameter, the values of the minimum and maximum slopes. If you multiply these values by 100, you will get these figures in centimeters.

Important! All these values can be used for arranging slopes exclusively on flat areas(that is, without connection to outlet pipes, siphons and other systems).

Wastewater system location

There are two wastewater systems:

Internal. This is a set of pipelines that ensure the removal of existing wastewater from plumbing devices and their removal outside the building. Most often, owners of private houses arrange such a system on their own. Fortunately, the construction market offers a wide range of different plastic elements.
An external wastewater system ensures the delivery of wastewater from the building to the septic tank (storage and treatment complex).

Internal piping

In addition to the slope of the internal sewerage system by 1 meter (SNiPom recommended values), the following recommendations must be adhered to:

We use pipes with a diameter of 100, 80, 50 or 40 mm (and a diameter of 100 mm is used to connect zones general purpose, that is, in places where pipelines converge).

We make the most optimal slope values for pipes of these diameters, namely: 0.015, 0.2, 0.03 and 0.035, respectively.
If according to technological process it is necessary to use adapters (for example, when moving from bigger size to a smaller one) we do this in such a way that the evenness of the lower part of the channel is not disturbed. Otherwise, the continuity of water flow may be disrupted.
We provide the required slope using fastening systems or the slope of the box in which we install the sewer system.

On a note! We make sure to maintain the required slope when installing the pipeline from the device to the sewer system. Moreover, we equip the turn to such a system with a tee or elbow (the inclination should be about 70 degrees).

We do not allow pipes to bend at right angles. We use exclusively bends (at 45 degrees and only).

On a note! If the pipe is of insignificant length, then deviation from a certain slope is quite acceptable.

External piping

In addition to the slope of the external sewer system by 1 meter (SNiP recommended values), the following recommendations must be adhered to:

Depending on the soil and climatic conditions, the depth of the trench can vary between 100-200 cm.
To correctly carry out the required slope, do not forget to take into account the ever-increasing recess. To do this, we initially make the depth deeper by 25 centimeters, so that it is convenient to arrange a sand support for the system.

We carry out the line at a depth below the freezing level (350 mm). When laying above the level, it is worth considering enhanced thermal insulation.
The diameter of the pipes used is 110-200 mm. In this case, the minimum slope is: 200 mm - 7 mm, 160 mm - 8 mm. But according to SNiP, the sewer slope per 1 meter (110 mm pipe in diameter) is about 20 mm.

Remember! If you want the slope to be most effective, follow the rule: the slope is no more than 150 mm (based on each linear meter).

We place the pipes at the same level, without changing the slope along the entire length.

Remember! It is unacceptable to combine pipes of different diameters. Also, level differences in the gasket should not be allowed. If such a need arises, then the installation of a manhole is mandatory.

Storm sewer

Function storm sewer- drainage of melt and rain flows (to avoid waterlogging of the area and preserve the foundation of the building).

In addition to the slope of 1 meter (SNiP recommended values), other factors must be observed, namely: the type of drainage system and the diameter of the pipe.

On a note! The minimum slope for drainage of melted water should be as follows: 7 mm (for pipes with a diameter of 200 mm) and 8 mm (for 150 mm).

In addition, other points need to be taken into account: characteristics local soil, average precipitation for the region of residence and the volume of wastewater.

Pipe configuration

Is the condition of a sewerage slope of 1 meter (SNiP recommended values) the only one for high-quality operation of the sewage system? No. There is one more important condition, without which blockage is inevitable. This is the configuration of the laid pipeline. After all, if it is too “sophisticated” and has a large number of bends, then wastewater will not be able to quickly flow (without lingering inside the pipes) into the collector, and then straight into wastewater treatment plants. In this case, no sewer slope of 1 meter (SNiP recommended values) will save the situation.

Pipe material

Can be:

plastic;
cast iron;
concrete;
asbestos-cement;
ceramic.

Most often, for the construction of an internal sewer system they use plastic pipes, and for the outside - asbestos-cement, cast iron or corrugated.

Finally